Wills Map

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Wills References

  • Wills, Christopher & Gutierrez, Carlos & Perez, Ante & Branum, David. (2015). A Next Generation V S 30 Map for California Based on Geology and Topography. Bulletin of the Seismological Society of America. 105. 10.1785/0120150105.
  • Wills 2015
  • Wills 2006 - C.J. and Clahan, K.B., [2006], Developing a map of geologically defined site-conditions categories for California: Bull. Seism. Soc. Am., Vol. 96 pp. 1483 – 1501

Description of Wills Digital Map

The supplementary data of the Wills et al. (2015) paper provides the map as a GIS shapfile (http://www.seismosoc.org/Publications/BSSA_html/bssa_105-6/2015105-esupp/index.html). I then rasterized it to a binary floating point file (which similar to the 2006 file, except with floats instead of short ints) using the gdal_rasterize command (http://www.gdal.org/gdal_rasterize.html). The command to rasterize it is:

gdal_rasterize -a Vs30_Mean -tr $RES $RES -l wills_2015_vs30_projected -of EHdr -ot Float32 ./wills_2015_vs30_projected.shp ./raster_$RES.flt

Where $RES is the grid spacing in degrees.

The original and rasterized data is stored here on opensha.usc.edu:


I suggest you use raster_0.00025.flt, which is rasterized with 0.00025 degree spacing (~25 meters). The raster_0.00025.hdr file contains the necessary coordinates for georeferencing it, but I'll summarize here:

The first location in the file is at:

x/longitude/ULXMAP = -124.406528862058
y/latitude/ULYMAP = 42.0090923024621

This is the upper left (northwest) point in the map.

numX/numLon/NCOLS = 41104
numY/numLat/NROWS = 37900

Grid spacing (both X and Y): 0.00025 degrees

Data type: 4-byte/32-bit little-endian floating point numbers

Mesh ordering: fast XY, so the first few points are:

    Index 0 (at byte 0): -124.406528862058, 42.0090923024621
    Index 1 (at byte 4): -124.406528862058+0.00025, 42.0090923024621 = -124.406278862058, 42.0090923024621
    Index 2 (at byte 8): -124.406528862058+0.0005, 42.0090923024621 = -124.406028862058, 42.0090923024621

Comparison of Wills Map 2006 versus 2015

These two wills maps were made from gis files released by the state.

Wills Map 2006
Wills Map 2015

These two wills maps are extracted by ucvm. The etree vs30 values are based on wills 2006, so we expect to see data from above in these maps.

Vs30 Map based on UCVM Etree for 2006
Wills Map 2015


Background information from


Where we worked at in generating the ucvm.e that we are currently using:


Created a configure file sample.conf

# grid2etree UCM Map config file

# Domain corners coordinates (degrees): 
proj=+proj=aeqd +lat_0=36.0 +lon_0=-120.0 +x_0=0.0 +y_0=0.0 

# Domain dimensions (meters): 

# Spacing 

# Etree parameters and info 

# Grid data directories 

NOTE: the ucvm.e newly recreated is 1.2G but UCVMC's ucvm.e is 683M

command used to generate ucvm.e

./grd2etree -f sample.conf

new ucvm.e

A new ucvm.e is created by replacing the vs30_hr_dir with the rasterized data file from Kevin and update the hdr file to match with what is expected by grd2etree

LAYOUT         BIL
nrows          37900
ncols          41104
NBANDS         1
NBITS          32

#ULXMAP         -124.406528862058
#ULYMAP         42.0090923024621
xllcorner         -124.406528862058
yllcorner         32.534092
cellsize          0.00025
NODATA_value  -9999
byteorder     LSBFIRST
XDIM           0.00025
YDIM           0.00025

Verify using CCA+GTL

With fixed scale
no GTL
With fixed scalebar,
GTL, with Original ucvm.e
GTL, with recreated ucvm.e
GTL, with ucvm.e with Wills 2015
With variable scalebar,
GTL, with Original ucvm.e
GTL, with recreated ucvm.e
GTL, with ucvm.e with Wills 2015

command used to generate the plots,

./plot_horizontal_slice.py -b 33,-123 -u 39.5,-115 -d vs -c cca -a sd -s 0.05 -e 0 -o cca.png

Verify using vs30 etree map

With variable scale
GTL, with recreated ucvm.e
GTL, with. ucvm.e with Wills2015

command used to generate the plots,

./plot_vs30_etree_map.py -b 33.5,-119 -u 34.5,-117 -s 0.0005 -c cca -a sd_r -o cca_vs30_etree_new.png

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